Backfire protective device



Oct. 31, 1950 D. L. MILLER 2,528,160

BACKFIRE PROTECTIVE DEVI CE Filed Sept. 23, 1946 3 Sheets-Sheet 1 IN V EN TOR.

wmwocmw m 124 A TTORNE Y WITNESS Oct. 31, 1950 D; L. MILLER 2,528,160

BACKFIRE PROTECTIVE DEVICE Filed Sept. 23, 1946 3 Sheets-Sheet 2 iii i55 ii 9&5

O IN V EN TOR. WITNESS: 6 flmaldfilillw OHNE Y Oct. 31, 1950 D. MILLER 2,528,160

BACKFIRE PROTECTIVE DEVICE Filed Sept. 23, 1946 3 Sheets-Sheet 5 IN VEN TOR.

WITNESS: BY 5237}. $77 1%; %ZWV TORNEY Patented Oct. 31, 1950 BACKFIRE PROTECTIVE DEVICE Donald L. Miller, Pine City, N. Y., assignor to Bendix Aviation Corporation, Elmira Heights, N. Y., a corporation of Delaware Application September 23, 1946, Serial No. 698,611

9 Claims.

The present invention relates to a backfire protective device for engine starters, and more particularly to a mechanically actuated switch mechanism for preventing actuation of the starting mechanism while the engine is rotating backward.

It is an object of the present invention to provide a novel mechanism for preventing actuation of an engine starter while the engine is rotating or rocking backward.

It is another object to provide such a device which may be arranged to prevent actuation of the starter whether the engine is rotating backward or forward.

It is another object to provide such a device which, after cranking has commenced, will not interrupt the cranking operation. I It is another'ebjeet to providesuch a device which may be actuated by any exposed moving part of the engine or its auxiliaries.

It i another object to provide such a device incorporating a two-stage starter control.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a semi-diagrammatic illustration of a preferred embodiment of the invention, the starting switch and control mechanism being shown partly broken away and in section;

Fig. 2 is a side view of the starting switch and control mechanism partly broken away and in section, showing the parts in idle position;

Fig. 3 is a detail of the control mechanism showing the parts in cranking position;

Fig. 4 is a view similar to Fig. 1 showing a second embodiment of the invention;

Fig. 5 is a side view of the starting switch and control mechanism shown in Fig. 4, the

parts being shown in the positions assumed when the control switch is initially closed while the engine member is stationary;

Fig. 6 is a detail similar to Fig. 5 showing the parts in the positions assumed when the control switch is actuated during backward rotation of the engine part;

4. A lead 5 connects the starting switch with the starting motor SM which is grounded at 6 to complete the starting circuit.

The starting switch 4 is provided with a solenoid l, energization of which is controlled primarily by the operator, and secondarily by an automatic means for preventing such energization when the engine to be started is rotating backward. As here shown, this is accomplished by means comprising a manual switch 8 connected to battery I by a lead 9, and connected by a lead II to a backfire protective device indicated generally by numeral I2. This device comprises a casing I3 containing a solenoid I4, with a magnetic plunger I5 slidably mounted therein Within a bearing member I6. The plunger IS is finormall maintainedin its upper position as shown in Fig. 1 by meansof a spring I1, and carries on its lower end aninsulated contact l8. A yoke member I9 is slidably mounted on the magnetic plunger [5 ad-v jacent its lower end, being retained thereon by a cap 2i which serves as the mount for the contact I8. A pin 22 is arranged to traverse the yoke I9 and is slidably mounted at its ends in guideways 24, 25 formed in the lower end of the casing I3.

An arcuate contact carrying member 23 of suitable insulating material such as fiber is pivotally mounted on the pin 22 and carries on its arcuate surface a curved contact element 26 which is normally spaced slightly from the contact I8, but may be engaged thereby when the plunger moves downward through the yoke I9. The yoke is normally held in extended relation to the plunger by means of a spring 21 located on the plunger above the yoke I9, so as to maintain contacts I8, 26 disengaged.

Means for normally maintaining the contact carrying member 23 in alignment with the plunger I5 is provided in the form of a tension spring 28 attached as indicated at 29 and 3| to the contact carrying member and the yoke I9 respectively.

The lower end of the contact carrying member 23 has a block 32 of suitable frictional ma terial such as fiber fixed thereto as by means of a coupling member 33. The block ,32 is arranged to project beyond the housinglg and a flexible diaphragm or boot 3 3 is preferably em-- ployed to close the lower end of the casing while permitting longitudinal and pivotal movement of the coupling member 33. V I

The casing I3 is provided with abinding post 35 to which the lead II of the control circuit is attached, and this binding post is connected by a lead to one end of the solenoid i i. The opposite end of the solenoid is connected by a lead 31 to a binding post 38 which is grounded as indicated at 39 to complete the circuit for energizing solenoid l4. Binding post 35 is also connected by a lead 41 to the contact l8, and the arcuate contact 28 is connected by a lead 42 to a binding post 43 which is connected by a lead 44 to one end of solenoid l of the magnetic starting switch 4, the opposite end of which is grounded as indicated at 5 to complete the control circuit for the starting switch.

The backfire protective device 12 is mounted as illustrated adjacent a moving part 45 of the engine to be started or of an auxiliary mechanism actuated thereby, so that the fiber block 32 will engage the moving part 45 when the magnetic plunger I5 is actuated. The device 12 is so mounted that the axis of the pin 22 forming the pivotal mount for the fiber block 32 is parallel to the axis of the engine part 45, and rotation of the engine part in a forward direction as indicated by the arrow in Fig. 3 thus causes the contact carrying member 23 to be rotated in a clockwise direction as there shown. The contact 26 is arranged to extend from the upper portion of the contact carrying member 23 a sufficient distance to maintain its engagement with the contact I8 during such clockwise movement of the contact carrying member. Counterclockwise movement of the member 23 due to backward rotation of the engine part moves the contact 25 out of the path of contact 18, however, so as to hold open the control circuit for the magnetic starting switch 4.

In the operation of thisembodiment-ottheinvention, starting with the parts in the positions illustrated in Fig. l, closure of the manual switch 8 causes energization of the solenoid l4 which pulls the plunger l5 downward. This motion is transmitted through the spring 2'! to the yoke member I9, thus moving the fiber block 32 into engagement with the engine part 46. If the engine is stationary at the time, the upright position of the contact carrying member 23 is maintained and further downward movement of the plunger [5, after the movement of the contact carrying member 23 is thus arrested, causes the contact 18 to engage the contact 26, thus completing the control circuit for the starting switch 4, causing closure thereof to actuate the starting motor. The consequent rotation of the engine part 46 causes the contact carrying member 23 to swing around its pivot pin 22 in a clockwise direction as shown in Fig. 3 but this pivotal movement does not interrupt the control circuit, so that the cranking operation is continued. When the engine starts, opening of the control switch by the operator causes the parts to return to normal position.

If, when the control swtich 8 is closed, the engine part 46 is rotating backward due to a backfire or for any other reason, when the fiber block 32 engages said part, the contact carrying member 23 is rotated in a counterclockwise direction thus moving the contact 26 out of the path of contact !8 whereby the control circuit for the starting switch is held open. As soon as the backward movement of the engine parts ceases, a reactuation of the starter control will cause energization of the starting mechanism in the usual manner.

In the embodiment of the invention illustrated in Figs. 4, 5 and 6, means are provided for pr venting actuation of the starting mechanism while the engine to be started is rotating or rocking in either direction, and additional means are incorporated to prevent interruption of the cranking operation after it has commenced.

As shown in Fig. 4, the starting system comprises a battery 5| grounded at 52 and connected by a lead 53 to a magnetic starting switch 54 which in turn is connected by a lead 55 to the starting motor SM which is grounded at 55 to complete the starting circuit. The backfire protective device indicated generally by numeral 51 comprises a casing 58 containing a solenoid 59 and a magnetic plunger 61 slidably mounted therein. The plunger is normally maintained in its upper position as shown in Fig. 1 by a sprin 62 and carries on its lower end an insulated contact 63 by means of a spring arm 64. A yoke 65 is pivoted on a pin 68 which is slidably mounted in slots 81, 68 in the lower end of the casing 58. The upper portion of the yoke 65 is attached as indicated at 69 to a pin 10 slidably mounted in the lower end of the plunger 61 and retained therein by suitable means such as a cotter pin ll traversing slots l2, '13 therein. The pin H3 is normally held in extended relation to the plunger 5! by means of a spring 14.

A contact carrying member 15 is pivotally mounted on the pin 66 within the yoke 65 and has on its upper end a contact 15 which is in the path of movement of the contact 63 when the member 15 is in upright position as shown in Figs. 4 and 5. Means for normally holding the member in such upright position is provided in the form of a coil spring 1'! anchored at its ends to the member 15 and the yoke 65 a respectively.

The backfire protective ctr/item is mounted adjacent a moving part 18 of the engine in such manner that when the solenoid 59 is energized the movement of the plunger 6| causes the contact carrying element 15 to engage said moving part, and to be rotated thereby, if the engine is in motion at that time, so as to move the contact I5 out of the path of contact 63.

The starting switch 54 is arranged to be actuated by an electromagnet l9, and a control circuit therefor is provided comprising a manual switch connected by a lead 8| to the battery 5| and by a lead 82 to a binding post 83 mounted on the casing 58. A lead 84 connects the binding post 83 to one end of the solenoid 59, the opposite end of the solenoid being connected by a lead 85 to a binding post 86 which is grounded at 81. Lead 84 is also connected by a lead 88 to the contact 63, and the contact 18 is connected by a lead 89 to a binding post 90 which is connected by a lead 9| to one end of electromagnet 19, the opposite end of which is grounded as indicated at 92 to complete the control circuit for the starting switch.

In order to prevent interruption of cranking due to the forward rotation of the engine part l8 by the starting motor, a holding resistor 93 is bridged across the leads 82, 9! of the control circuit, the value of the resistor being such as to pass sufficient current to hold the starting switch closed, such current being insufficient however to effect initial closure thereof.

In the operation of this embodiment of the invention, closure of the manual switch 83 efiects energization of the solenoid 59, causing the plunger 6! to move downward, bringing the contact carrying member 15 into engagement with the engine part 18. If the engine is stationary at the time, the upright position of the contact carrying member is maintained, and further movement of the plunger 6I causes the contact 63 to be brought into engagement with the contact 16, thus completing the control circuit for the starting switch which is thus actuated to energize the starting motor. The consequent rotation of the engine part 18 by the starting motor causes the contact carrying element 15 to be rotated on the pin 66 so as to disengage the contact 16 from the contact 63. Energization of the electromagnet 19 is, however, maintained sufficiently by the current flowing through resistor 93 tohold the starting switch 54 closed and prevent interruption of the cranking operation. When the engine starts, opening of the control switch 80 by the operator causes the parts to return to idle position.

If, when the control switch 80 is initially closed, the engine is rotating or rocking in either direction, such motion of the engine part 18 will'cause pivotal movement of the contact carrying member 15 as soon as it engages said part, thereby moving the contact 16 out of the path of contact 63 so as to hold open the control circuit and prevent actuation of the starting mechanism.

The contact carrying element 15 i preferably shaped as illustrated so that when it has been swung out of its upright position by motion of the engine part 18 in either direction, it will maintain its displaced position irrespective of reversalSOf movement of the engine part 18, so that actuation of the starting mechanism cannot take place until the operator has deenergized the solenoid 59 and then caused reenergization thereof. This is desirable since it prevents the possibility of the aCtllation cilire QlgltihgIHQChanism during*'-a'back"- r66k of the engine after forward rotation thereof has ceased.

. 'In Fig. 7 of the drawing, there is illustrated an embodiment of the invention incorporating a twostage starter control, that is, one in which the starting motor is initially energized by a reduced voltage from the battery, the full voltageof the battery being applied to the starting motor after such initial energization thereof. As illustrated, the starting circuit comprises a battery IOI grounded at I02 and connected by a lead I03 to a magnetic starting switch I04. Switch I04 is connected by a lead I05 to a resistor I06 having such a value as to reduce the voltage of the battery sufficiently to properly control the initial actuation of the starting motor. Resistor I06 is connected by a lead I01 to the starting motor SM which i grounded at I08 to complete the starting circuit.

. A second electromagnetic switch I09 is provided for short-circuiting the resistor I06 as well as the starting switch I04, and for this purpose is connected by a lead l I I to the battery lead I03, and by a lead I I2 to the starting motor lead I01.

Starting switch I04 is arranged to be actuated by a solenoid I I3, and the second magnetic switch I09 is similarly provided with a solenoid II4. Means are provided for controlling both these solenoids so as to prevent energization of the starting circuit when the engine is rotating in either direction, and further to secure closure of the second magnetic switch by the initial rotation of the engine after closure of the starting switch I94. For this, purpose, a solenoid H5 is mounted in a casing H6, and a magnetic plunger I I1 is slid-ably mounted in the solenoid by means of a bearing H8 inposition to be drawn downward into the solenoid against the pressure of a spring H9. The lower end of the plunger II1 has fixed thereon a cup member. I2I carrying an insulated contact I22. A yoke member I23 is slidably mounted on the plunger H1 and is normally pressed against the contact carrying cup I2I by a compression spring I24. A pin I25 traverses the lower ends of the yoke arms and is slidably mounted at its ends in guideways I26, I21 formed in the interior of the casing I I6.

A movable contact carrying member I28 is pivotally mounted on the pin I25 and carries on its upper end a contact I29 which is normally maintained in the path of the contact I22 by means of a tension spring I3 I' attached at its ends to the contact carrying member I28 and the yoke I23 as indicated at I32 and I33 respectively. The contact carrying member I28 also carries adjacent its upper end a second contact I34 which is movable into the path of the contact I22 when the contact carrying member is rotated in a clockwise direction as shown in Fig. 8.

A friction block I35 of suitable material such as fiber is mounted on the lower end of the contact carrying member I28 as by means of a connector I36 in position to project out ofthe casing H6, and the lower end of the casing is preferably closed by means of a flexible boot I31. The casing H6 is mounted adjacent a movable part I38 of the engine to be started, in such position that the friction block I35 will be moved into engagement with the engine member by the initial movement of the plunger I I1 when the solenoid H5 is energized, whereby the contact carrying member I28 will be moved about its pivot I25 in a clockwise direction when the engine is rotating forwardly as indicated by the arrow in Fig. 8.

@filtundenthecontrohof the operator for energizing the solenoid H5 is provided comprising a manual switch I39 connected to the battery lead I03, and by a lead I4I to a binding post I42 on the casing II6. Binding post I42 is connected by a lead I43 to one end of the solenoid II5, the opposite end of which is connected by alead I44 to a binding post I45 which is grounded as indicated at I46.

In order to provide a control circuit for sole- I noid II 3 of the starting switch I04, one end of the solenoid is connected by a lead I41 to the battery lead I03, andthe opposite end is connected by a lead I48 to a bindingpost I49 on the casing H6. Binding post I49 is connected by a lead I5I to the contact I29. Contact I22 is connected by a lead I52 to the grounded binding post I45 to complete said control circuit.

Similarly, solenoid I I4 for the second magnetic switch I09 is connected by a lead I53 to the starting circuit lead I05, and by a lead I54 to a binding post I55 on the casing I I6, which binding post is connected by a lead I56 to the contact I34 on the contact carrying member I28.

In operation, closure of the manual switch I39 completes the circuit through the solenoid I'I5 whereby the plunger- H1 is drawn downwardly, the yoke I23 with the contact carrying member. I28 being connected to move with the plunger by the spring I24. When the friction block I 35 engages the engine member I38, the downward movement of the contact carrying member I28 and the yoke I23 is arrested whereby the further downward movement of plunger I I1 brings the contact I22 into engagement with the contact carrying member I28. If at this time the engine member is stationary, the contact I29 is in the path of contact I22, and the control circuit for the solenoid II 3 of the starting switch is completed through contacts I29, I22 to the ground whereby the starting switch IE4 is caused to close and energize the starting motor from the battery IUI at a reduced voltage by virtue of the resistor I06. Initial rotation of the engine member I38 by the starting motor causes the friction block I35 to swing the contact carrying member I28 in a clockwise direction as shown in Fig. 8 thereby bringing the contact I34 into engagement with contact I22 thus completing the control circuit for the second magnetic switch I05 which thereupon closes and connects the starting motor directly to the battery thus utilizing the full battery voltage to crank the engine. It will be understood that the space between the contacts I29 and I34 is less than the width of the cooperating contact I22 whereby the latter bridges said space and causes closure of magnetic switch IE9 prior to the opening of the starting switch I04. After the starting switch opens, the control circuit for the magnetic switch IE9 is maintained fully energized by current supplied to the starting motor lead I85 through the magnetic switch I89 and resistor I85. Since the current drain through this control circuit is very small compared to the cranking current, the voltage drop through the resistor I 96 under these circumstances is negligible, and the solenoid H4 is maintained fully energized as long as the manual switch I39 is held closed. When the engine starts, the manual switch I39 is opened and the parts returned to their idle positions as illustrated in Fig. '7.

If, when the manual switch I39 is first closed, the engine is rotating rearwardly because of a previous backfire, or for any other reason, when the fi lbtfirfbldck ifi engages the moving engine member I38, it will cause the contact carrying member I 28 to swing in a counterclockwise direction, thereby moving the contact I29 out of the path of contact I 22. The further movement of contact I22 thus causes it to engage the contact carrying member I28 without completing the control circuit for solenoid I I3 through contact I29, whereby the starting mechanism is prevented from being energized. Likewise, if when the manual switch It!) is closed, the engine is rotating in a forward direction, the block I35 will swing the contact carrying member I 23 in a clockwise direction so that when the contact I22 engages the contact carrying member, it makes connection with the contact I 34 instead of the contact I29. Inasmuch as contact I34 is at this time dead, since the starting switch I04 has not closed, the starting mechanism is again prevented from being energized.

Although certain embodiments of the invention have been shown and described in detail, it will be understood that other embodiments are possible and that various changes can be made in the design and arrangement of the parts illustrated without departing from the spirit of the invention as defined in the claims appended hereto.

What is claimed is:

1. In an engine starting system, an electrical circuit, closure of which causes actuation of the starting mechanism, said circuit comprising a pair of normally open contacts, means under the control of the operator for moving one of the contacts toward the other and means actuated by a moving part of the engine for displacing the second mentioned contact from the path of the movable contact.

2. In an engine starting system, a starting cir-' cuit including a magnetic starting switch, a control circuit for the starting switch including a pair of normally open contacts, means under the control of the operator for moving one of the contacts into engagement with the other to close the control circuit, means responsive to movement of a member of the engine to be started for moving the second contact out of the path of the first contact, and means for preventing the automatic deenergization of the starting switch by forward movement of the engine member.

3. In an engine starter, a starting circuit including a battery, a starting motor, manually controllable means for applying part of the voltage of the battery to the motor, and means responsive to initial forward rotation of the engine for applying the full voltage of the battery to the motor.

4. In an engine starter, a starting circuit, a battery, a startin motor, manually controllable means for applying a part of the voltage of the battery to the motor, and unitary means responsive to backward rotation of the engine to prevent energization of the starting motor, and responsive to forward rotation of the engine for applying the full voltage of the battery to the starting motor.

5. An engine starter as set forth in claim 4 including further, means responsive to forward rotation of the engine, for preventing initial energization of the starting motor.

6. In an engine starter, a starting circuit including a battery, a starting motor, a starting switch, and a resistor for reducing the voltage from the battery applied to the starting motor upon closure of the starting switch, and means responsivato initial forward rotation of the engine after closure of the starting switch for short-circuiting said resistor.

7. An engine starter as set forth in claim 6 including further, means responsive to rotation of the engine in either direction for preventing closure of the starting switch.

8. In an engine starter, a starting circuit including a battery, a starting motor and electromagnetic starting switch, and a resistor for reducing the voltage from the battery applied to the starting motor by closure of the starting switch, a control circuit for the starting switch, a second electromagnetic switch for connecting the starting motor directly to the battery, a control circuit for the second electromagnetic switch including said starting switch, means responsive to rotation of the engine in either direction for preventing closure of the control circuit for the starting switch and means responsive to forward rotation of the engine for completing the control circuit for the second electromagnetic switch through the starting switch.

9. An engine starter as set forth in claim 8 comprising further, means including a manual switch for controlling the energization of both control circuits.

DONALD L. MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 18,897 Devine July 18, 1933 Re. 22,385 Coffey Oct. 26, 1943 (Other references on following page) Number 9 Name Date Richards Mar. 7, 1916 Bijur June 17, 1919 Kratz et a1 Feb. 15, 1921 Cowen Aug. 9, 1921 Yonge May 15, 1923 Goodheim June 26, 1923 Ross Dec. 1, 1925 Hajek Oct. 19, 1926 Howsam Feb. 19, 1935 Drabin Apr. 28, 1936 Number 10 Name Date McGrath Feb. 16, 1937 Liverance, Jr May 10, 1938 Liverance, Jr. June 28, 1938 Garber Sept. 29, 1942 Matthias Sept. 29, 1942 Dermond Aug. 10, 1943 Baker Feb. 13, 1945 Miller Apr. 10, 1945 Lee Aug. 19, 1947 

